1. Field of Invention
The present invention relates to a camera and particularly to cameras using self developing film.
2. Description of the Prior Art
Various types of self-developing film sheets instant cameras using such films are known.
For example, U.S. Pat. No. 3,682,076 discloses a self developing type film in the form of sheets and a bag containing self developing solution. When the film is taken out of the camera after exposure, the bag containing the developing solution is broken, and the developing solution coming out of the bag is spread over the film to develop the latter. Here, a plural number of film sheets are put in a film cartridge one over the other, while a film cartridge is loaded in the camera. On the other hand, the instant photographic camera using the aforementioned film cartridge is disclosed in U.S. Pat. No. 3,689,262. In case of this camera, the sensitive sheets in the film cartridge are exposed one by one in such a manner that when the sensitive material on each sheet has been exposed, the exposed sheet is taken out of the camera by means of a film transport. The sensitive material is then led through press rollers in the transport mechanism, and the bag containing the developing solution in sheet is broken under the pressure of the press rollers in such a manner that the developing solution coming out of the bag is spread over the surface of the sensitive sheet material. When the sheet travels through the press rollers, the developing solution is spread evenly over the surface of the sheet. Generally the aforementioned transport mechanism, is driven by a motor. When the mechanism is for example, manually driven, the driving speed varies from time to time, the developing solution is not spread evenly over the sensitive material and the speed influences the development. Thus, the mechanism of this kind of the camera is driven with a motor, which runs evenly.
This kind of camera excells in the speediness, namely the photograph taken can be seen on the spot, so that the camera is often used for example at parties, when photographs taken are handed over to the participants. Here the objects are often dark and are often in motion. When an object is photographed in a dark place for example by means of a camera with electronic shutter, the shutter time becomes longer in proportion to the darkness of the object and therefore the exposure time becomes longer and the photograph is out of focus. Thus, in such a case it is necessary to provide a speed light, i.e., flash, device in such a manner that the shutter time does not become longer than a certain value. Namely there are many opportunities to use the flash with this kind of camera, so that it is convenient to build the flash into the camera.
However, this kind of the instant photographic camera is by far larger and less portable than those using 35 m/m roll film. In conventional cameras the problem of the camera size is solved by connecting the photographic lens and the camera body with means such as bellows. When a photograph is to be taken, the bellows are extended so that the length of the optical axis is proper for photographing between the photographic lens and the camera body. When the camera is not in use the bellows are shortened so as to bring the photographic lens part close to the camera body. Thus, it is important to make the instant photographic camera compact. For example the battery to be loaded should be small in number as well as in shape. Thus in order to economize the space for the battery to be loaded in the camera, generally only one battery is loaded in the camera so as to drive other devices in the camera. For example, the only one battery loaded in the camera serves to drive not only the film transport device but also the exposure control device. Even when an electronic flash is provided, it is desirable to avoid providing a battery exclusively for the flash, because otherwise the size of the camera would become larger.
Hence, even when a flash device is provided or built in this kind of camera, it is desired that the current supply to the film transport device and the speed light device should be made from a single common battery in order to make the camera compact, because in this way the space occupied by batteries can be limited. However as soon as the sheets of sensitive material have been exposed in this kind of camera the film transport device starts to operate, while the flash unit also starts to charge as soon as the device has operated. However, this applied a large load to the power source.
Thus, when the flash device is charged immediately after flash photography while the sensitive material transportation device is driven, there is a fear that the motor may not start for a while. Further, even if the motor starts to rotate, there is a fear that the rotation speed may be low and unstable.
The above is a large problem in case of the instant photographic camera in which a self developing type film is used. Namely, in an instant photographic camera it is desirable that immediately after the exposure, namely the shutter operation the exposed sensitive material could be taken out of the camera and the photograph taken could be seen. Further unless the exposed sensitive material in sheet would be transported at a constant speed by means of the sensitive material transportation device, the exposed sensitive material would not be developed in a proper way, influencing the result of the development in an inprofitable way.